During the past year, over 540 peptides have been produced by the Branch largely for preparing peptide antisera and for defining MHC class I or class II restricted T cell epitopes. Proteins for which peptides have been provided to make antisera include plasma sialoglycoprotein (Sg p120); Il-8; HB9, a human homeodomain containing protein; P. faciparum G6PD, tubulin and Duffy receptors; CD4; SIV; Herpes simplex virus I; Il-10; C-jun; CD3 proteins; CD40; Igm`; P. gallinaceum pgs 28; and a human neutrophil G-protein. Sources of proteins for which peptides have been provided to define T cell epitopes include HIV, HTLV-1, CMV, murine leukemia viruses, influenza viruses, myelin basic protein, Vaccinia proteins, Sendai virus, MCMV, respiratory syncytial virus, and VSV. For functional studies, peptides have been provided that correspond to regions of HIV REX protein, and the HIV TAT protein, that can act as substrates for protein kinases, and that can mimic neutrophil NADPH oxidase activity. Within the Branch, synthetic peptides have to be used to prepare antisera to a variety of integrins and to define the binding specificity of HLA-A2, HLA-B27, HLA-A3 and HLA-DQw5 molecules. Moreover, peptide epitopes recognized by patient's sera were defined for HTLV-I and HTLV-II. In some cases, these reactives can be used to distinguish HTLV-I from HTLV-II infection.